8 Things You Didn't Know About Your Penis

Sensitivity, pleasure, size, and other surprising facts.

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2. Your Penis May Be a 'Grower' or a 'Show-er' continued...

A penis that doesn't gain much length with an erection has become known as a "show-er," and a penis that gains a lot is said to be a "grower." These are not medical terms, and there aren't scientifically established thresholds for what's a show-er or a grower.

Kinsey's data suggest that most penises aren't extreme show-ers or growers. About 12% of penises gained one-third or less of their total length with an erection, and about 7% doubled in length when erect.

3. The Pleasure Zone

Many men consider the underside of the glans (head) of the penis and the underside of the shaft to be most sensitive to sexual pleasure.

Researchers asked 81 healthy men to rate the erotic sensitivity of different areas of their bodies, including not only the penis but also zones such as the scrotum, anus, nipples, and neck.

The underside of the glans and underside of the shaft had the highest sensitivity rating for a significant majority of men, followed by the upper side of the glans, left and right sides of the glans, sides of the penis, upper side of the shaft, and foreskin (for the minority of men who were uncircumcised). The study findings were reported in the British Journal of Urology International in 2009.

4. Sensitivity Declines With Age

Studies show that the penis steadily loses sensitivity as men age though it's hard to say exactly by how much. That's because different researchers have used different ways to stimulate the penis and measure sensitivity.

In general, the sensitivity of the penis is gauged by the least amount of stimulation a man is able to feel. That is called the "sensory threshold."

Despite differences between studies, the data show a clear trend when taken together. From age 25 on, sensitivity starts to decline. The sharpest decline in sensitivity is seen between age 65 and 75.

What's less clear is whether men really notice a loss of sensitivity as they age.

Kohler says that if they are aware of it, his patients seldom mention it.

"It is a super-rare complaint," he says. "On the other hand, difficulty with erections and difficulty achieving ejaculation are much more common."